Good luck keeping a hand on your sleek iPhone. It’s like trying to hold onto a wet bar of soap! To protect your investment, try the Speck ToughSkin ($22 to $35: www.speckproducts.com), which has a thick rubber case, with a clear screen protector and a removable belt clip that doubles as a movie-viewing stand. Its straight sides and flat back actually improve the accuracy of the leveling tools (see the TiltMeter Pro app).